1. Field of the Invention
This invention relates to a pad for an air bag device for an automobile.
2. Description of the Prior Art
A conventional pad for an air bag device has an upper wall portion having openable portions which, upon expansion of an air bag, are separated from a side wall portion of the pad, leaving a hinge portion, and are angularly moved about the respective pivot axes so as to be opened.
The openable portions are composed of a net insert of a net-like structure and a covering layer of a soft synthetic resin material which covers the net insert (see Japanese Patent Unexamined Publication No. 63-182115).
As shown in FIG. 9, the net insert 1 has a base portion 2 which is embedded in the covering layer at the side wall portion of the pad, and upper portions 3 of rectangular shape extending from the base portion 2 and adapted to be embedded in the openable portions respectively. The opposite ends of the base portion 2 are connected together by sewing, so that the base portion 2 has a ring shape. Reference numeral 4 denotes a reinforcement cloth.
As shown in FIG. 10, when the covering layer is to be molded in an injection mold, the net insert 1 is set on a mold member 5 in such a manner that the base portion 2 is fitted on a predetermined portion of a mold member 5, with the meshes of the upper portions 3 engaged with set pins 6 fixedly mounted on the mold member 5. Then, the mold is closed, and the covering layer is molded.
As noted above, in the conventional pad for an air bag device, each upper portion 3 of the net insert 1 which is embedded in the openable portion of the pad is formed in a rectangular shape.
However, the upper wall portion of the pad is formed into a curved configuration. For that reason, the surface of the mold member 5 on which the set pins 6 are fixedly mounted is correspondingly curved. As a result, when the net insert 1 is set on the mold member 5 with the rectangular upper portions 3 engaged with the set pins 6, to mold the covering layer, wrinkles are liable to be produced in the upper portions 3.
When the covering layer is molded with the upper portions wrinkled, part of the upper portion 3 will be exposed, and a molding sink, a cavity, deformation or other defect will be produced in part of the covering layer. This adversely affects the appearance of the openable portion of the pad.
The foregoing phenomenon is not limited to the case where the upper wall portion of the pad is formed into a curved configuration, and can also occur when the side wall portion of the pad is formed into a curved configuration. Indeed, in that case wrinkles are also liable to be produced in the upper portions 3 of the net insert 1 when the net insert 1 is set on the mold member, thus adversely affecting the appearance of the openable portions of the pad.